It has been known in the past to provide one passage among two passages communicating with a combustion chamber of an internal combustion engine with a swirl control valve opening and closing the passage, and to control the opening and closing of this swirl control valve so as to change a strength of a swirl flow generated in the combustion chamber. In general, in an internal combustion engine, if the engine speed is low, the amount of flow of intake gas is small and therefore fuel and air are harder to mix. Accordingly, it is known to close the swirl control valve to generate a strong swirl flow in the combustion chamber, when the engine speed is low (for example, PLT 1).
In addition, even when the engine speed is low, when the load of the internal combustion engine (below, referred to as the “engine load”) is high, if closing the swirl control valve to generate a strong swirl flow in the combustion chamber, the “over swirl” is generated and thus cooling loss is increased. Therefore, it is proposed to open the swirl control valve when the engine load is high to suppress the swirl flow generated in the combustion chamber and thereby suppress an increase in the cooling loss (for example, PLT 1).